Upon a study by Freshbooks in 2010, the countries where their invoices are paid the earliest are China with 11.9 days, Mexico, South Africa, Australia, New Zeland, Germany and Spain. Among the big economies with the longest invoice payment times are Italy and Uniked Kingdom. The country were invoices take longer to be paid is India with 31.7 days.
Interactive Things produced a visualization to illustrate the average days to pay:
Freshbooks are a provider of online billing systems mostly for freelancers, small businesses and service providers. As such, their data reflect well how the great mass of companies that make the wheels of the economy work are paid by others of their size and also by the large corporate ones.
Also, this data is more relevant than research based on surveys, which are by design actively selecting the sampling effort based on minimum cost and profile of the customer/customers paying for the research. Freshbook data is a neutral snapshot of their database at a given point in time.